Injection drug users (IDUs) constitute 60% of the approximately 5 million people in the United States infected with hepatitis C virus (HCV), and the majority of drug users in opioid agonist treatment programs have HCV. Even though there are effective HCV treatments, alarmingly few drug users and opioid agonist maintained patients have initiated HCV treatment. Because HCV has a discrete course of treatment lasting only 24 to 48 weeks and its backbone is once-weekly subcutaneous pegylated interferon injections, it may be ideally suited for directly observed treatment (DOT) management. To test this, we have designed a small randomized controlled trial of modified DOT (mDOT) for HCV treatment (both pegylated interferon and ribavirin) in drug users enrolled in opioid agonist treatment. The goal of this mentored award is to enhance the clinical research skills of Alain Litwin, M.D., M.P.H., M.S., through research on integrating HCV treatment with substance abuse treatment. Dr. Litwin's training plan involves formal mentorship in the following areas: implementing comprehensive DOT programs in opiate agonist programs, measuring and analyzing adherence in drug users, designing behavioral interventions for drug users, clinical trial study design, advanced statistical methods, and community-based participatory research. The specific aims of this proposal are: (1) To determine in randomized trial whether modified directly observed HCV treatment (pegylated interferon alfa-2a plus ribavirin) provided on-site at a methadone program is more efficacious than self-administered HCV treatment for enhancing adherence; (2) To determine the impact of providing on-site HCV treatment on virologic outcomes, and to determine the association between HCV treatment adherence and virologic outcomes. As a sub-aim, we will also determine whether mDOT is more efficacious than self-administered HCV treatment for achieving HCV treatment outcomes; and (3) To identify individual-level factors (e.g. active drug and alcohol use, active psychiatric illness, housing status, social support, beliefs and knowledge about HCV medications, motivation to adhere, self-efficacy, and medication side effects) influencing HCV treatment adherence and HCV treatment outcomes. Findings from this project will be used to inform the development of a large randomized trial of the efficacy and cost-effectiveness of modified directly observed HCV care versus regular on-site care.